class Session(object):
  def __init__(self, global_id, session_id, reader, writer):
    self.global_id = global_id
    self.session_id = session_id
    self.reader = reader
    self.writer = writer
  
  def get_key(self):
    return Session._get_key(self.global_id, self.session_id)
  
  @staticmethod
  def _get_key(global_id:int ,session_id:int)->str:
    return '%d-%d'%(global_id, session_id)